The goal of communication systems is to convey information reliably from one physical location to another. Often information transmission needs to be performed at high speeds and power consumption needs to be low.
One communication scenario where this is the case is chip-to-chip communications where semiconductor components communicate with each other. Examples of such components are processors, memories and application specific integrated circuits (ASICs).
Communication is not perfect and some sources of imperfections are noise and non-idealities of the components making up the communication system.
The path between the source and destination of the information may be modelled by a communication channel or channel. The channel may include the effect of the main propagation medium, connectors and other circuit components or integrated circuits (ICs). As an example, the channel in digital subscriber line communications (DSL) may include a twisted pair of copper conductors and a connector that connects the twisted pair to the DSL modem. Furthermore, the channel may include the non-ideal characteristics of the DSL receiver front-end.
The channel may comprise one or multiple signal paths. The signal path is able to carry a physical quantity in the form of a signal. The information to be conveyed is represented by symbols that may be generated by a source. A symbol may be modulated into a signal that may be transmitted over the signal path. At the destination the signals on the signal paths are read and/or measured and a received symbol is extracted from which the original information may be recovered.
A signal path may be an electrical conductor, an electrical waveguide, an optical waveguide, etc. The signal path may include additional electrical and/or optical components and ICs.
In many scenarios communication takes place over a set of parallel signal paths that comprise electrical conductors. The theory of this setting of parallel electrical conductors is known to those of skill in the art and may be described by the theory of multi-conductor transmission lines (MCTL).
An example of an application where parallel signal paths that comprise conductors are used is server backplane communications. Many signal paths or pairs of signal paths are packed on a printed circuit board (PCB) to facilitate communications between e.g. CPU and memory. Another example is the use of silicon interposers or through silicon vias (TSVs) used to connect two or more semiconductor components.
One major issue with communication over parallel signal paths is that the signal paths interact with each other. In a communication setting where different signals are to be transmitted over each of the signal paths this leads to crosstalk between the transmitted and/or received signals.
Crosstalk often limits the capabilities of a communication system. For instance, crosstalk may limit the amount of information that can be transmitted reliably. Moreover, it may also limit the maximum rate at which information can be transmitted since crosstalk often becomes worse at higher transmission rates.
In many communication systems where multiple signal paths are present, the spacing between the signal paths must be large enough such that crosstalk is below an acceptable level. This limits the allowable density of the signal paths and the total bandwidth that can be obtained.
The disadvantage of many prior art approaches to mitigate crosstalk is that crosstalk is not cancelled completely. Moreover, the approaches to mitigate crosstalk by signal processing techniques lead to high implementation and hardware complexity. This is especially the case when the number of signal paths increases since for such signal processing methods complexity usually grows quadratically with the number of signal paths. This results in increased silicon footprint and power consumption, which makes these prior art approaches of limited use in e.g. high-speed chip-to-chip communications.
There is currently no system able to mitigate and/or cancel crosstalk between multiple signal paths completely and is efficient in terms of implementation and hardware complexity. Embodiments of the invention are directed toward solving these and other problems individually and/or collectively.